package com.dushiguang.findhoney.Utils.encrypt;

import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

/**
 * Created by ex-dushiguang201 on 2016-01-04.
 * AES加密
 */
public class AESUtils {
    public static final String HEX = "0123456789ABCDEF";
    public static final String AES_KEY = "f@103mfkcl;dkemckspsowq*039432";

    /**
     * 加密
     * @param key 密钥
     * @param src 加密文本
     * @return
     * @throws Exception
     */
    public static String encrypt(String key, String src) throws Exception {
        byte[] rawKey = getRawKey(key.getBytes());
        byte[] result = encrypt(rawKey, src.getBytes());
        return toHex(result);
    }

    /**
     * 加密
     * @param key 密钥
     * @param src 加密文本
     * @return
     * @throws Exception
     */
    private static byte[] encrypt(byte[] key, byte[] src) throws Exception {
        SecretKeySpec skeySpec = new SecretKeySpec(key, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(src);
        return encrypted;
    }

    /**
     * 解密
     * @param key
     * @param src
     * @return
     * @throws Exception
     */
    public static String decrypt(String key, String src) throws Exception {
        byte[] rawKey = getRawKey(key.getBytes());
        byte[] enc = toByte(src);
        byte[] result = decrypt(rawKey, enc);
        return  new String(result);
    }

    /**
     * 解密
     * @param key 密钥
     * @param encrypted 解密文本
     * @return
     * @throws Exception
     */
    private static byte[] decrypt(byte[] key, byte[] encrypted) throws Exception {
        SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec);
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

    public static byte[] toByte(String hexString) {
        int len = hexString.length() / 2;
        byte[] result = new byte[len];
        int i;
        for (i = 0; i < len; i++) {
            result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2),16).byteValue();
        }
        return result;
    }

    /**
     * 获得256位密钥
     * @param seed
     * @return
     */
    private static byte[] getRawKey(byte[] seed) {

        try {
            KeyGenerator kgen = KeyGenerator.getInstance("AES");
            SecureRandom sr = null;
            if (android.os.Build.VERSION.SDK_INT >= 17) {
                sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
            } else {
                sr = SecureRandom.getInstance("SHA1PRNG");
            }
            sr.setSeed(seed);
            kgen.init(256, sr);
            SecretKey skey = kgen.generateKey();
            byte[] raw = skey.getEncoded();
            return raw;
        } catch (Exception e) {
            e.printStackTrace();
        }

        return null;
    }

    public static String toHex(byte[] buf) {
        if (buf == null) {
            return "";
        }
        StringBuffer result = new StringBuffer(2 * buf.length);
        int i;
        for (i = 0; i< buf.length; i++) {
            appendHex(result,buf[i]);
        }
        return result.toString();
    }

    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
    }
}
